[1] MacMillan played club rugby for Edinburgh University, West of Scotland[2] and London Scottish.
Five Scots were selected for Middlesex: Gregor MacGregor, George Campbell, William Wotherspoon, MacMillan and Frederick Goodhue, all with London Scottish who played in the county.
[6] MacMillan played international rugby for Scotland for over 11 seasons, and in 1891 he represented the British Isles team on their South Africa.
He was killed when out on a fox hunt in 1936 with the Vale of White Horse Hounds in Cirencester Park.
For the most part MacMillan's estate went to his wife; most of the rest to other family, he had no children; but some of the bequests on his death went to his servants depending on their length of service.